The present invention relates to a data communication network for interconnecting a plurality of control computers mounted on a vehicle utilizing a data communication line.
There has been a recent trend to computerizing various vehicle systems. Often there are a multiplicity of control computers such as an engine control computer for controlling the operation of the vehicle's internal combustion engine in a highly accurate manner, a transmission control computer for automatically controlling a transmission device and a speed control computer for regulating a travelling speed to a desired value. Heretofore, these control computers have functioned independently. This requires much wiring duplication because often multiple computers are wired to the same sensor because they need the same information.
To cope with this problem, a network system for vehicles is utilized. Data is communicated among computers by linking on a common data communication line. However, in a motor vehicle there are problems in sharing data by various computers. First, various types of computers have already been developed. These computers are used in different "combinations". Secondly, some of these computers are marketed as optional products. As the number of optional products utilized increases, data flowing on the communication line increases in volume. The transfer of control data among the individual computers becomes inadequate.
If the data communication rate among the computers is fixed so as to allow for the maximum number of optional control computers, i.e. the highest volume of data possible, the communication data rate must be quite high. However, at high data rates, data cannot be transmitted error free in a motor vehicle environment. There are increased influences caused by electromagnetic noise or the like generated from the engine, the electromagnetic noise causing data corruption in the communication line. As a result, communication among the computers becomes unreliable.